Answer:
Unit rates for cyclist A , B, C , D are 12 mile/ hour , 5 mile/hour, 9 mile/hour and 10 mile/hour respectively. Cyclist A is the fastest among the four.
Step-by-step explanation:
Cyclist A can ride 24 miles in 2 hours
so, cyclist A's unit rate is, 
= 12 mile/hour
Cyclist B's unit rate is, 
= 
= 
= 5 mile/hour
Equation for cyclist C is, y = 9x ,
so, cyclist C's unit rate is , 9 mile/hour
Slope of the graph for cyclist D,
= 
= 10
So cyclist D's unit rate is, 10 mile/hour
So, cyclist A is the fastest.